The invention relates to optical fiber interconnects having offset ends.
Optical fiber interconnects are often subjected to the ends being offset. Such an offset can be due to the inability of an employed technology to ensure a low enough misalignment of the interconnect ends, or can be an essential feature of a particular photonic package design. If the offset is substantial, it leads to a reactive tensile force in the fiber. This force occurs because the ends of the interconnect cannot move closer to compensate for the greater length of the deformed fiber. The reactive tensile force not only results in a tensile stress in the fiber, but also, more importantly, can lead to a significant increase in the bending stress. The adverse consequences of the tensile stress can be even greater, if the interconnect is subjected to the additional, xe2x80x9cactivexe2x80x9d, tension. Such a tension can be due, for instance, to the thermal expansion mismatch between the low expansion glass and the relatively high expansion material of the enclosure, when the structure is heated up for reflow soldering, during a laser welding operation, or during temperature cycling. Elevated tensile stresses and curvatures may have an adverse effect on interconnect mechanical strength and transmission losses. The situation is different, however, in the case of compression. Interconnect compression can be caused, for example, by the thermal contraction mismatch of the glass with the material of the enclosure, when the structure is cooled down from a manufacturing temperature to a lower room or testing temperature.
It is, therefore, desirable to minimize optical fiber interconnect bending to achieve lower tensile stresses and curvatures which may improve mechanical strength and minimize transmission losses.
A method is disclosed of fabricating a structure comprising an optical fiber interconnect adhesively soldered or epoxy bonded into a ferrule inside an enclosure. An illustrative embodiment of the method comprises selecting an enclosure material such that a compressive force caused by the thermal contraction mismatch of the glass fiber with the material of the enclosure during the cooling of the structure minimizes tensile stress in the interconnect. Cooling may be for example, from a manufacturing temperature to room temperature.
Further disclosed are an optical fiber interconnect structure and a semiconductor device fabricated according to the method.